John s



(No Model.)

J. S. STONE. TELEPHONE SIGNALING CIRCUIT.

No. 563,692. Patented July 7, 1896.

UNITED STATES PATENT EEicE.

JOHN STONE, GE 1308' ON, MASSACHUSETTS, ASSIGNOR TO THE AMERICAN BELL TELEPHONE COMPANY, OF SAME PLACE.

TELEPHONE SIGNALING-CIRCUIT.

SPECIFICATION forming part Of Letters Patent NO. 563,692, dated July 7, 1896.

Application filed March 18, 1896. Serial No. 583,794. (No model.)

To caZZ whom it may concern:

Be it known that I, JOHN S. STONE, residing at Boston, in the county of Suffolk and State of Massachusetts, have invented certain Iniprovcmcnts in Telephone Signaling-Circuits, of which the following is a specification.

In branch terminal telephone-exchange systems employing automatic calling apparatus a common centralized battery is normally connected with the substation-circuits through the line'signal, and the circuit being through the call-bell at the substation when the telephone is upon the hook-switch the armature of the bell is constantly attracted to the core of one of the belhhelices and acquires a tendenoy to adhere thereto, so that it is'technically said to become locked or biased, and when a substation callingcurrent is sent through the circuit from the central station the bell-armature fails to respond and the hell does not ring.

The object of the present invention is to provide means whereby this fault is overcome, and the bell-armature made free to respond to the signaling-current.

In such substation-circuits as those to which I refer the circuitconductors are provided with normally open branch terminal switch connections upon each switchboard-section, and each conductor passes through a coil or winding in the line-signal to the poles of a common battery, and ordinarily in grounded circuits to prevent the substation-call-bell armature from thus becoming biased the bell-magnet is placed in series with a condenser, while in metallic circuits it is placed either in series with a condenser or in a branch to ground. There are objections to these devices, which need not be described here.

This invention permits the substation callbell to be placed directly in the circuit when the telephone is on its hookswitch support, while the line-signal has a portion of its windings placedin series with each conductor, and the common battery for signaling the central station is connected directly with the said conductors, and it comprises the arrangement of the operators plug-and-cord circuits in such manner that when a plug is inserted in a socket and the ringing-key is depressed the common central battery which furnishes current for incoming call-signals is introduced or placed across the circuit in a second branch in a direction opposite to that in which it is already connected through the line-signal, whose coils also serve as impedances and resistances, so that the biasing effect of the battery is neutralized, and the call-bell armature is made free to respond to current from the special generator which provides current for outgoing calls and which is automatically switched to the circuit by the depression of the ringing-key. Ohcourse the same object would be attained in substantially the same way if the insertion of the plug and the concurrent operation of the key were made to connect the circuit in question with the opposite poles of an independent battery of like power, and since such a construction would clearly embody the spirit of the invention.

In the drawings, Figure 1 is a diagram of a substation-circuit and a portion of the operators cord-circuit, both in a normal or quiescent condition. Fig. 2 is a similar diagram, the operators apparatus being arranged for calling the substation; and Fig. 3 is a schematic drawing illustrating the operation of the circuits shown in Fig. 2.

L is the substation-circuit, whose conductors a and Z) extend from the substation A to the central station E. The conductor a connects the hook-switch l with one coil or winding section in of the line-signal or annunciator D, and to the negative pole of the common signaling-battery, which has a low internal resistance, and conductor Z2 connects the contact 2 and the bell C with the second coil-section m of the winding of the signal appliance D to the positive pole of the batteryE. Branch terminal jacks or plug-sockets J represent the circuit upon the respective sections of the switchboard. As much of the operators cord-circuit as is necessary to illustrate the invention is shown, and consists of a plug P, whose tip 8 is connected by Wire '7 with spring 12 of the ringing-key 7n, and whose sleeve 9 connects by wire 6 with the opposite spring 13. The spring 10 of the key is united by wire g, including resistance 'r, to point 20, and the complementary spring 11 is united by wire 19, through resistance T to one terminal of the substation calling-generator G, the other terminal of which is connected by wire f with point 21.

In the operation of the invention, when a substation is to be called, the plug P is insorted in a socket J, its tip 8 making contact with the spring 11 and its sleeve 9 with the spring h. This does not affect the relation of the batteryE and the substation-bell Gas long as the key remains unoperated, because, as clearly indicated in Fig. 1, the cord--conductors 6 and 7 terminate in the springs 12 and 13, at both of which the circuit is open. When, however, the said key is depressed, as shown in Fig. 2, a new relation isbrought about, for

- the said springs 12 and 13 are thereby forced into contact with their associate springs 10 and 11, the former of which, by wire g and resistance 'r, connects with the negative pole, and the latter, through wire 19, resistance 1' and the calling-generator G, with the positive pole of the battery E. The result of this is that while the battery E still maintains its normal connection with the substation callbell 0 (its positive pole. being connected therewith through main conductor 1), and its negative pole through main conductor a) a second connection is also established between the said battery and call-bell, in which the polar arrangement of the former is reversed, the positive pole now being also connected with the bell through conductor a and the negative pole through conductorb. This second route for the battery-current is traceable from its positive pole through point 21, conductor f, generator Gr, wire 19, resistance 7*, key-springs 11 and 13, conductor 6, plugsleeve 9, socket -spring h, branch 22, main conductor a, bell 0, main conductor (2, branch,

23, socket-spring i, plug-tip 8, conductor 7, key-springs 12 and 10, wire g, resistance r, and point 20 to the negative battery-pole.

It is evident that during the operation of the key other branch circuits for the batterycurrent are likewise formed, which divert a portion of the said current in any case from the main line. One of these leads from the positive to the negative pole of the battery through point 21, section m of the annunciator, branch 23, socket-spring 'i, plug-tip 8, conductor 7, key-springs 12 and 10, wire g, resistance 1', and point 20; and another unites the said poles through conductor f, generator G, wire 19, resistance r key-springs 11 and 13, conductor 6, plug-sleeve 9, socket-spring h, branch 22, conductor a, section m of annunciator-winding, and point 20. All of these several circuits are more easily traceable in the diagram, Fig. 3. By this arrangement, as already stated, a portion of the batterycurrent is diverted from the substation-line and through the said derived circuits; and such portion of current as would remain to otherwise pass through the main circuit in a given direction, and which would therefore tend to maintain the undesired quiescence of the bell-armature, is neutralized by a substantially equal current which in virtue of my invention passes through the main circuit and substation call-bell oppositely when the key is depressed to send the outgoing call; or, more properly speaking, the operation of said key impresses upon the main circuit by means of the original source of current an electromotive force substantially equal in strength but opposed in direction to the electromotive force already impressed upon such circuit by the same source in its normal connection, and a zero of unidirectional current through the bell is thereby produced as long as the key remains depressed, though; the battery connection is maintained. When the key 70 is pressed,'the calling-generator G is also introduced and an alternating current is sent through they circuit as follows: start ing from the right side of the generator by wire 19, resistance 7*, springs 11 and 13, wire 6, sleeve 9 of plug P, spring h of socket, branch wire 22, conductor a, bell O, conductor b, branch wire .23, spring 1' of socket, tip 8 of plug P, wire 7, springs 12 and 10 of key, wire 9, and resistance 'r to point 20, bridge 5, and battery E to point 21, and by wire f to the other side of the calling-generator; and the bell O,bein g untramnieled by current from the battery E, responds readily and promptly to current from generator G.

When the plug is inserted and the key is depressed, the entire organization may be regarded as a signaling-circuit, constituted of the original substation-circuit, and the operators keyboard circuit or loop.

The alternating currents of the call-generator traverse this circuit, as already explained, while for the time and as long as the key is depressed the annunciator-coil m is brought into a bridge or shunt circuit between the points 22 and 20, and the annunciator-coil m into a similar circuit'between the points 23 and 21.

The coils m m of the line-signal D are made to oifer a considerable impedance to the alternating currents from the calling-generator, which therefore is not appreciably diverted through them.

The function of the resistances r r is to balance the calling-circuit, as when the fall of potential from battery E through 7' 7' and generator G is equal to the fall of potential from battery E through the coils 'm m there will be no potential from generator E impressed upon the circuit a 1).

Having now fully described the invention, I claim 1. The combination of a telephone-circuit extended between a substation and a central station, and containing a polarized bell at the former and switch connections. at the latter station; and a battery at the central station normally and constantly connected directly with the conductors of said circuit and impressing thereon an electromotive force of constant direction; with means for connecting the poles of the same or an equal battery reversely with the said circuit-conductors, through the switch connections thereof, and for therebyimpressing an equal and opposite electromotive force upon said circuit; substantially as, and for the purposes described herein.

2. In combination with a telephone-circuit extended between two stations, a polarized call-bell connected therewith at one station, switch connections at the other station, and a battery constantly connected with the two conductors of said circuit directly, and normally maintaining a current of given direction through said bell; a normally open loop extending to the said circuit-conductors from the opposite poles respectively of the said battery through the said switch connections, and a circuit-closing key in the said loop con trolling the continuity thereof, and adapted when operated to neutralize the normal linecurrent,by an opposed current of like strength from the same source, substantially as described.

3. The combination of a polarized call-bell at a substation, and switch connections, a battery and a circuit-closing call-key at a central station, with a main telephone-circuit extending between the said stations, the two conductors of such circuit having a direct permanently-closed connection with the two poles respectively of the said battery, and a normally open connection through the said switch connections and key, each with an opposite pole thereof; whereby when the said keyis operated the said battery is enabled to impress equal and opposite electromotive forces upon the circuit, and to produce there in a zero of battery-current.

i. A telephone-circuit extended between a substation and a central station, a polarized call-bell connected therewith at the former station, and switch connections, and a battery whose poles are constantly connected with the 1nain-circuit conductors direct, at the latter station, normally maintaining a current in the said circuit; combined with a normally open loop or operators circuit extending to the said circuit-conductors from the opposite poles respectively of the said battery, through the said switch connections, an alternating-current call-generator in the said operators circuit adapted to furnish current for the operation of said bell, and a circuitclosing call-key also contained therein controlling the continuity thereof, the reverse current of the battery, and the operation of the call-generator, substantially as specified.

5. The combination substantially as here inbefore described of a telephone-exchange metallic circuit extended between a central station and a substation, an electric bell responsive to alternating currents at the substation in the said circuit, a signal-receiving instrument having half of its winding in one and half in the other conductor of said circuit, a battery connected directly with the conductors of said circuit. and supplying current in a definite direction thereto, and switch connections for said circuit all at the central station, with a normally open opcrators keyboard circuit or loop adapted for connection with the said keyboard-circuit at its switch connections, an alternating-current call-generator, the said battery, and a call-sending key controlling the batteryterminals, and the continuity of the call-generator. circuit, all included in said loop; the said batteryhaving its poles connected with the key so that when the said hey is operated to transmit call-currents to line, it is enabled simultaneously to supply a battery-current to line in a direction opposite to that supplied to the line by the same battery direct.

6. In a telephone-exchange system, a signaling-circuit formed of a substation-circuit provided with branch terminal switch-socket connections in discontinuous bridges at the central station, and an operators keyboard circuit or loop terminating in a switch plug inserted in one of the said sockets, a polarized call-bell in said circuit at the substation an alternating call-generator at the central station to actuate the same; a circuit-closing and signal-sending key controlling the said generator; a battery having two independent connections with the said circuit, one in which its poles are permanently united to the conductors thereof to supply a normal current of definite direction thereto,and the other through the call-key and plug and socket, in which the polar connection is reversed with respect to the said conductors to supply an equal and neutralizing current to the said circuit, when the said key is operated to actuate the call-generator; and a callannunciator in the said circuit having a portion of its winding in each main conductor thereof at points between the permanent battery connections, and the switch-socket connections to constitute impedance-coils, operating to prevent the short-circuiting of the alternating generator call-currents all substantially as specified and for the purposes set forth.

7. In a telephone-exchange, a signalingcircuit consisting of a telephone substationcircuit, and an operators normally open keyboard circuit or loop; the former provided at the substation with a call-bell, and at the central station with discontinuous bridges includingbranch terminal spring-j acks, a lowresistance battery having its poles in permanent connection with the ends of its conductors, and with a call-receiving annunciator having coils of high impedance, one of which is located in each of the said conductors, be tween the spring-jacks, and the battery, and the latter comprising a plug inserted in one of the said spring-jacks, a ringing-key, an alternating-current generator to send outgoing calls, and equalizing or balancing resistances; the key connections being such, that when the said key is depressed the oall-generator, a reversed battery, the equalizing resistances and the substation call-bell are all placed in said spring-jack having in series with its tip and sleeve conductors the said battery 20- I 5 versed, a calling-generator, and two balancing resistances, as set forth.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 13th day of 20 March, 1896.

JOHN S. STONE.

Witnesses:

GEo. WILLIS PIERCE, JosEPE A. GATELY. 

